Returns the filesystem path for a fetched handle. Raises an error if the handle has not been fetched yet.
See also
on_handle() to create a handle, on_fetch() to materialize.
Examples
if (FALSE) { # \dontrun{
handle <- on_handle("ds000001")
handle <- on_fetch(handle)
path <- on_path(handle)
list.files(path)
} # }